This invention relates generally to axle disconnects for part-time four wheel drive vehicles and more particularly to vacuum operated axle disconnects.
U.S. Pat. No. 5,105,900 granted to Randy W. Adler and David Sperduti Apr. 21, 1992 discloses a part time four wheel drive vehicle that includes an axle disconnect mechanism in a front axle assembly. The axle disconnect mechanism includes a vacuum motor and a shift fork assembly. The vacuum motor communicates with a vacuum source (not shown) that is controlled by a two position solenoid valve. The fork shift assembly under control of the vacuum motor controls the axial shifting of a clutch collar between positions corresponding to coupled and uncoupled operating modes.
U.S. Pat. No. 5,102,902 granted to Robert J. Wilson and Randolph C. Williams Apr. 21, 1992 discloses the same axle disconnect mechanism.
The two systems have the common drawback of an externally mounted vacuum motor that requires considerable extra space particularly when vehicle suspension travel is taken into account. The use of an externally mounted vacuum motor also necessitates the use of a fork shift assembly which adds to the cost and complexity of the prior art arrangement exemplified by these two patents.
U.S. Pat. No. 5,123,513 granted to Harry A. Petrak Jun. 23, 1992 also discloses a part time four wheel drive vehicle that includes an axle disconnect in the front axle assembly. This axle disconnect is operated by a power shift mechanism. The power shift mechanism includes sealed envelopes in the form of expandable and contractible compartments that shift the axle disconnect into and out of engagement in response to a remote control valve. The sealed envelopes are located in the axle housing encircling a shiftable drive gear as shown in FIG. 7 of the patent. The shiftable drive gear couples and uncouples inner and outer drive shafts.
This arrangement does not require the extra space and fork shift assembly of the previous arrangement. However, this arrangement requires two sealed envelopes and several other parts operatively connecting the sealed envelopes with the shiftable drive gear. Consequently this arrangement is also complex and expensive to produce particularly when the difficulty of assembly is taken into account.